WO2023074234A1

WO2023074234A1 - Method for manufacturing spherical glass particles, burner, spherical glass particles and composition for dental use

Info

Publication number: WO2023074234A1
Application number: PCT/JP2022/036116
Authority: WO
Inventors: 匡志中村; 潤木下
Original assignee: 日本電気硝子株式会社
Priority date: 2021-10-28
Filing date: 2022-09-28
Publication date: 2023-05-04

Abstract

A method for manufacturing spherical glass particles that comprises: a dispersion step for crushing agglomerated particles containing agglomerated non-spherical glass particles by passing the agglomerated particles through a dispersion nozzle (50) and injecting the non-spherical glass particles from the dispersion nozzle (50); and a spheronization step for heating the non-spherical glass particles injected from the dispersing nozzle (50) to thereby spheronize the non-spherical glass particles.

Description

Method for producing spherical glass particles, burner, spherical glass particles and dental composition

The present invention relates to a method for producing spherical glass particles, a burner, spherical glass particles and a dental composition.

Patent Document 1 describes a resin composition in which a curable resin contains glass particles.

JP 2020-73333 A

In such resin compositions, glass particles capable of obtaining good physical properties are desired. Specifically, the glass particles are preferably spherical particles with a small diameter, and there is a demand for a technique for obtaining such particles at a high yield.

Means for solving the above problems and their effects will be described below.
A method for producing spherical glass particles which solves the above-mentioned problems is a method for producing spherical glass particles using non-spherical glass particles as a main raw material, wherein agglomerated particles containing the agglomerated non-spherical glass particles are passed through a dispersion nozzle. a dispersing step of crushing the aggregated particles and spraying the non-spherical glass particles from the dispersing nozzle; and heating the non-spherical glass particles sprayed from the dispersing nozzle. and a spheroidization step of spheroidizing.

In the method of manufacturing spherical glass particles, the dispersion process is followed by the spheroidization process. Therefore, in the method for producing spherical glass particles, the spheroidizing step can be performed on non-spherical glass particles that are more dispersed than aggregated particles. Thus, the method for producing spherical glass particles can produce spherical glass particles that are fine and spherical.

In the method for producing spherical glass particles, it is preferable that in the dispersing step, the aggregated particles are crushed by colliding the aggregated particles with a collision member provided in the dispersion nozzle.
In the method for producing spherical glass particles, non-spherical glass particles can be obtained by colliding aggregated particles with a collision member.

In the method for producing spherical glass particles, the spheroidization step preferably heats the non-spherical glass particles by applying flames from a burner to the non-spherical glass particles ejected from the dispersion nozzle.

The method for producing spherical glass particles can easily melt the surface of the non-spherical glass particles in the spheroidizing step.
In the method for producing spherical glass particles, the non-spherical glass particles in the dispersed state preferably have a particle diameter of 2.0 μm or less when a cumulative value of 50% is measured by laser diffraction scattering particle size distribution measurement. In the present specification, D50 refers to the particle size when the volume-based cumulative value is 50% in the particle size distribution measured by laser diffraction/scattering particle size distribution measurement. In the following description, this term will be used without special mention.

A burner for solving the above problems is a burner for processing agglomerated particles including agglomerated non-spherical glass particles, comprising a burner nozzle having a fuel injection port for injecting fuel, a dispersing section for crushing the agglomerated particles, and a dispersion nozzle having a powder injection port for injecting the non-spherical glass particles crushed in the dispersion unit, wherein the fuel injection port is arranged to surround the powder injection port. be.

The burner can apply flames to the non-spherical glass particles injected from the dispersion nozzle. Therefore, since the burner can heat the non-spherical glass particles immediately after being crushed, it is possible to obtain spherical glass particles having a fine particle size and having a spherical shape.

The spherical glass particles that solve the above problems are spherical glass particles that have a fire-polished surface on their surface, and have a particle diameter at a cumulative value of 50% in the particle size distribution measured by laser diffraction scattering particle size distribution measurement. is 2.0 μm or less.

The spherical glass particles having the above structure can increase the filling rate in the resin material and improve the dispersibility in the resin material. As a result, physical properties of the resin composition can be enhanced.
The spherical glass particles preferably have a specific surface area of 25.0 m ² /g or less.

Spherical glass particles are composed of SiO ₂ : 20 to 80%, Al ₂ O ₃ : 1 to 30%, B ₂ O ₃ : 0 to 20%, BaO+CaO: 0 to 40%, and ZnO: 0 in terms of % by mass as a glass composition. -20%, F: preferably 0-25%.

A dental composition that solves the above problems comprises the spherical glass particles described above and a photocurable resin.
The dental composition having the above structure can have improved physical properties.

According to the above configuration, it is possible to obtain spherical glass particles that can exhibit good physical properties when contained in a resin.

FIG. 1 is a schematic diagram of an apparatus for producing spherical glass particles. FIG. 2 is a cross-sectional view schematically showing a burner of the manufacturing apparatus. FIG. 3 is a front view of the burner. FIG. 4 is an enlarged sectional view of the dispersion nozzle of the burner. FIG. 5 is a process diagram of a method for producing spherical glass particles. FIG. 6 is a table comparing physical properties of spherical glass particles of Comparative Examples and Examples. FIG. 7 is an image of spherical glass particles of Comparative Example 1-2. FIG. 8 is an image of the spherical glass particles of Example 1-1. FIG. 9 is a table comparing physical properties of dental materials of Examples and Comparative Examples. FIG. 10 is an image of the dental material sample of Example 2-1. FIG. 11 is an image of the dental material sample of Example 2-2. FIG. 12 is an image of the dental material sample of Comparative Example 2-1. FIG. 13 is a table comparing physical properties of dental compositions of Examples and Comparative Examples.

An embodiment relating to spherical glass particles is described below.
<Spherical Glass Particle Manufacturing Apparatus>
As shown in FIG. 1, an apparatus for producing spherical glass particles (hereinafter referred to as "particle production apparatus 10") includes a reservoir 21, a feeder 22, a first transport path 23, a carrier fluid supply source 24, A second transport path 26 , an oxygen supply source 27 , a fuel supply source 28 and a burner 30 are provided.

<Storage unit 21>
The storage part 21 is a tank that stores non-spherical glass particles, which are the main raw material of the spherical glass particles. The non-spherical glass particles are crushed glass particles obtained by crushing a base glass of arbitrary shape such as plate-like, film-like, ingot-like, or fiber-like with a crusher such as a ball mill or a jet mill. , which are shaped particles with corners and peaks. Inside the reservoir 21, the non-spherical glass particles are aggregated. Agglomeration of non-spherical glass particles does not occur intentionally, but occurs due to interaction of non-spherical glass particles. In the following description, aggregates containing secondary particles in which non-spherical glass particles that are primary particles are aggregated are also referred to as aggregated particles. Aggregated particles may contain primary particles that are not aggregated in addition to secondary particles, or may contain higher-order particles in which secondary particles are further aggregated. The proportion of secondary particles in aggregated particles may be less than the proportion of primary particles in aggregated particles.

<Feeder 22>
Feeder 22 is connected to reservoir 21 . The feeder 22 supplies aggregated particles stored in the storage section 21 to the first transport path 23 . The feeder 22 is preferably capable of adjusting the amount of aggregated particles supplied per unit time.

<First transportation path 23 and second transportation path 26>
The first transportation path 23 connects the feeder 22 and the second transportation path 26 . The second transport path 26 connects the first transport path 23 and the burner 30 . A carrier fluid supply 24 is connected to a second transport line 26 . Carrier fluid source 24 delivers carrier fluid to second transport path 26 . As carrier fluid is delivered from the carrier fluid supply 24 to the second transport path 26 , the carrier fluid transports the agglomerated particles to the burner 30 . The carrier fluid is, for example, air, and is a gas or medium having fluidity capable of carrying aggregated particles in a suspended state.

A preliminary disperser can be installed between the feeder 22 and the burner 30. The preliminary disperser should be appropriately selected from dispersers capable of crushing aggregated particles, such as fluidized bed dispersers, rotary drum dispersers, ejector dispersers and venturi dispersers. can be done.

<Burner 30>
Burner 30 is configured for processing agglomerated particles. The burner 30 includes a burner nozzle 40 that injects fuel, and a dispersion nozzle 50 that injects the aggregated particles while crushing them. In the following description, in the burner 30, the upstream side in the moving direction of the passing aggregated particles is the base end, and the downstream side is the tip.

<Burner Nozzle 40>
As shown in FIGS. 2 and 3, the burner nozzle 40 includes a tubular first outer peripheral wall 42 and a second outer peripheral wall 43, a disk-shaped first partition wall 44 and a second partition wall 45, and a tubular wall. and a plurality of rectifier tubes 47 formed. The burner nozzle 40 also has an oxygen supply chamber R1 to which oxygen is supplied and a fuel supply chamber R2 to which fuel is supplied.

The inner diameter of the first outer peripheral wall 42 is larger than the outer diameter of the second outer peripheral wall 43 . The first outer peripheral wall 42 has a connection port 421 connected to the oxygen supply source 27 . The second outer peripheral wall 43 has a connection port 431 connected to the fuel supply source 28 . The first partition wall 44 is joined to the base end portion of the first outer peripheral wall 42 . The second partition wall 45 is joined to the base end portion of the second outer peripheral wall 43 . The first peripheral wall 42 houses the second peripheral wall 43 , which houses the dispersion nozzles 50 . At this time, the second outer peripheral wall 43 penetrates the first partition 44 and the dispersion nozzle 50 penetrates the second partition 45 . The plurality of rectifying tubes 47 are bundled. A plurality of straightening tubes 47 are arranged in a ring between the second outer peripheral wall 43 and the dispersion nozzle 50 . A plurality of rectifying tubes 47 rectify the gas flow passing through the tubes.

As shown in FIG. 2, the oxygen supply chamber R1 is partitioned by a first outer peripheral wall 42, a second outer peripheral wall 43 and a first partition 44. Oxygen is supplied from the oxygen supply source 27 to the oxygen supply chamber R1 through the connection port 421 . When oxygen is supplied to the oxygen supply chamber R1 , oxygen flows out from between the first outer peripheral wall 42 and the second outer peripheral wall 43 .

The fuel supply chamber R2 is partitioned by the second outer peripheral wall 43 and the second partition wall 45. Gaseous fuel is supplied from the fuel supply source 28 to the fuel supply chamber R2 via the connection port 431 . In the burner nozzle 40 , when fuel is supplied to the fuel supply chamber R2 , the fuel is injected from the fuel injection port 48 between the second outer peripheral wall 43 and the dispersion nozzle 50 . Thus, the burner nozzle 40 can inject flame from the fuel injection port 48 by igniting the fuel injected from the fuel injection port 48 .

<Dispersion nozzle 50>
As shown in FIG. 4 , the dispersion nozzle 50 includes a tubular conduit 51 and a nozzle cover 53 that covers the tip of the conduit 51 .

The outer diameter of the conduit 51 is smaller than the inner diameter of the second outer peripheral wall 43 of the burner nozzle 40 . A second transport path 26 is connected to the proximal end of the conduit 51 . The conduit 51 has a nozzle 511 with an enlarged inner diameter at its tip. The nozzle cover 53 has a disk-shaped collision member 531 and a plurality of powder injection ports 532 . Impact member 531 includes an impact surface 533 . In this embodiment, the collision surface 533 is a plane orthogonal to the axial direction of the conduit 51, but in other embodiments, the collision surface 533 may be a cylindrical surface or a conical surface. . As shown in FIG. 3, when the nozzle cover 53 is viewed from the tip, the powder injection port 532 has an arc shape. The plurality of powder injection ports 532 are arranged at intervals in the circumferential direction. A plurality of powder injection ports 532 surround the collision member 531 .

As shown in FIG. 4, the dispersion nozzle 50 is constructed by connecting a conduit 51 and a nozzle cover 53 in the axial direction. Specifically, the nozzle cover 53 covers the tip of the conduit 51 . At this time, the opening surface of the nozzle 511 of the conduit 51 faces the collision surface 533 of the nozzle cover 53 .

As shown in FIG. 2, the dispersion nozzle 50 is housed in the burner nozzle 40. Specifically, the dispersion nozzle 50 is integrated with the burner nozzle 40 by being inserted into the cylindrical second outer peripheral wall 43 of the burner nozzle 40 . At this time, the tip of the nozzle cover 53 and the tip of the fuel injection port 48 of the burner nozzle 40 are flush with each other. As shown in FIG. 3 , the powder injection port 532 is surrounded by the fuel injection port 48 . Further, the powder injection port 532 and the fuel injection port 48 open in the same direction.

In the dispersion nozzle 50 , the aggregated particles supplied from the second transport path 26 are crushed by colliding with the collision member 531 . In this respect, the collision member 531 corresponds to an example of a "dispersion section", and the dispersion nozzle 50 can be said to have a collision-type disperser. By colliding with the collision member 531, most of the aggregated particles are crushed into non-spherical glass particles, which are primary particles. Then, the crushed non-spherical glass particles are injected from a plurality of powder injection nozzles 532 .

<Method for Producing Spherical Glass Particles>
As shown in FIG. 5, the method for producing spherical glass particles (hereinafter referred to as "particle production method") includes a preparation step S11, a transportation step S12, a dispersion step S13, and a spheroidizing step S14.

The preparation step S11 is a step of preparing aggregated particles to be stored in the storage unit 21. The preparation step S11 includes a pulverization step of pulverizing the raw glass and a classification step of classifying the pulverized glass. The preparation step S11 may include at least a pulverization step.

The crushing process is, for example, a process of crushing plate-shaped raw glass with a crusher. In the particle production method of the present embodiment, fine spherical glass particles are produced using fine non-spherical glass particles as raw materials. Therefore, it is preferable to finely pulverize the raw material glass in the pulverization step. In the pulverization step, aggregated particles are obtained by unintentionally aggregating the non-spherical glass particles. Further, the degree of aggregation of the aggregated particles, in other words, the degree of dispersibility of the non-spherical glass particles in the aggregated particles does not matter.

The classification process is a process of classifying agglomerated particles by air classification, elutriation classification, mesh sieving, and the like. The classification step may be carried out for the purpose of removing coarse powder and the like contained in aggregated particles. Aggregated particles obtained by performing the preparation step S11 are stored in the storage section 21 .

By performing the preparation step S11, it is possible to obtain agglomerated particles containing agglomerates of non-spherical glass particles with fine and uniform particle diameters. Aggregated particles may have a D50 of "2.0 μm or less" in a dispersed state.

The transportation step S12 is a step of transporting the aggregated particles stored in the storage section 21 to the burner 30 . The transport step S12 drives the feeder 22 and causes the carrier fluid to flow from the carrier fluid supply source 24 into the second transport path 26 . Therefore, the transport step S12 transports the agglomerated particles to the burner 30 with a carrier fluid.

The dispersing step S13 is a step of crushing the aggregated particles by causing the aggregated particles transported by the carrier fluid to pass through the dispersion nozzle 50. Specifically, the dispersing step S13 is a step of crushing the aggregated particles by causing the aggregated particles to collide with the collision member 531 of the dispersion nozzle 50 . In the dispersing step S13, most of the aggregated particles are crushed into non-spherical glass particles, which are primary particles. In the dispersing step S13, it is preferable to crush all of the aggregated particles into non-spherical glass particles, but it is not necessary to crush all of the aggregated particles into non-spherical glass particles. In the dispersion step S13, the crushed non-spherical glass particles are injected from the powder injection port 532 of the dispersion nozzle 50 together with the carrier fluid.

The spheroidizing step S14 is a step of heating the non-spherical glass particles jetted from the dispersion nozzle 50 to spheroidize the non-spherical glass particles. Specifically, the spheroidizing step S14 causes flame to be injected from the fuel injection port 48 of the burner nozzle 40 . Then, in the spheroidization step S14, flames jetted from the burner nozzle 40 are applied to the non-spherical glass jetted from the dispersion nozzle 50 to sphere the non-spherical glass. In addition, since the spherical glass particles may aggregate, it is preferable to provide a classification step after the spherical forming step S14 in order to crush the aggregation.

<Spherical glass particles>
Spherical glass particles produced by the above-described particle production method will be described.
Since the spherical glass particles are heated in the spheroidizing step S14, they have fire-polished surfaces. The fire-polished surface may form part of the surface of the spherical glass particles, but preferably forms the entire surface of the spherical glass particles. Whether or not the spherical glass particles have a fire-polished surface can be determined by observing the surfaces of the spherical glass particles with a microscope or measuring the surfaces of the spherical glass particles with a measuring instrument.

Spherical glass particles can be rephrased as solid or non-porous glass particles. The spherical glass particles preferably have smooth surfaces free of corners, peaks, voids and cracks. Also, the fire-polished surface can be rephrased as a convex curved surface, a spherical convex surface, or a curved surface. The fire-polished surface is preferably a smooth surface free of corners, peaks, voids and cracks.

If the surface of the spherical glass particles is a fire-polished surface, the specific surface area tends to be small. The smaller the specific surface area of the spherical glass particles, the lower the viscosity of the dental composition obtained by mixing the resin and the spherical glass particles. As a result, the dental material obtained by curing the dental composition is less likely to contain bubbles, thereby suppressing a decrease in the strength of the dental material.

The sphericity, which indicates the degree of sphericity of spherical glass particles, is "0.5 to 1.0". The sphericity is preferably "0.7 or more", more preferably "0.8 or more", and even more preferably "0.85 or more". In the present embodiment, spherical glass particles having a sphericity of "0.5 or more" are called spherical.

The sphericity of at least 10,000,000 particles is measured by an image analyzer such as Verder Scientific Camsizer XT. can be calculated by substituting

Sphericality = 4π·S/d ²
More specifically, when calculating the sphericity, first, a microscope is used to photograph particles transported in the air by compressed air. Subsequently, the area and circumference of the particle are obtained by analyzing the captured image. Finally, the sphericity is calculated by substituting the obtained numerical value into the above formula. In the above measurement, the photographed particle becomes a two-dimensional plane circle, so it can be said that the degree of circularity is actually evaluated. However, measuring the shape of 10 million or more particles is synonymous with measuring the circularity of particles at all angles. Therefore, the above circularity statistically corresponds to sphericity. If the photographed particle is a true sphere, the sphericity will be "1.000".

Since the spherical glass particles are spherical, the specific surface area tends to be smaller than that of crushed particles. However, when the diameter of the spherical glass particles becomes smaller, the specific surface area of the spherical glass particles becomes larger. Accordingly, a dental composition in which spherical glass particles having a small particle size are mixed with a resin tends to have a high viscosity. Therefore, the dental material obtained by curing the dental composition may contain bubbles. In this case, there is a risk that the strength of the dental material will be reduced, or that the dental material will peel off from the cavity due to the deterioration of the adhesiveness between the dental material and the cavity. Specifically, this problem becomes apparent when the viscosity of the dental composition exceeds 1500 mPa·s. Therefore, in order to avoid this problem, the spherical glass particles preferably have a specific surface area of "25.0 m ² /g or less", more preferably "21.0 m ² /g or less", and "17 .0 m ² /g or less” is more preferable. Although the lower limit of the specific surface area is not particularly limited, it is practically "0.1 m ² /g or more". Here, the specific surface area is the specific surface area measured by the BET method.

In a dental material prepared by photocuring a dental composition in which a resin and spherical glass particles are mixed, if the D50 of the spherical glass particles is larger than 2.0 μm, the following problems arise. In other words, when a tooth is restored with a dental material, spherical glass particles are removed from the surface of the dental material due to occlusion adjustment, polishing due to morphology correction, and friction due to chewing after occlusion. A concave portion having a depth (Rv) of 1.0 μm or more is formed. When such dental materials are used, there is a problem that bacteria easily proliferate in the concave portions of the dental materials, and tooth decay is likely to occur. On the other hand, when the D50 of the spherical glass particles is less than 0.5 μm, there is a problem that the manufacturing cost of the spherical glass particles increases significantly. Therefore, in order to avoid these problems, the spherical glass particles have a D50 of "0.5 to 2.0 μm", preferably "0.8 to 1.5 μm". Further, the spherical glass particles preferably have a refractive index of "1.48 to 1.62".

Spherical glass particles, as a glass composition, SiO ₂ : 20 to 80%, Al ₂ O ₃ : 1 to 30%, B ₂ O ₃ : 0 to 20%, BaO + CaO: 0 to 40%, ZnO: 0-20%, F: 0-25%. Preferably, the glass composition of the spherical glass particles is SiO ₂ : 40 to 80%, Al ₂ O ₃ : 1 to 30%, B ₂ O ₃ : 2 to 20%, and CaO: 0 to 25% in mass %. , ZnO: 0-10%, Li ₂ O: 0-10%, Na ₂ O: 0-30%, K ₂ O: 0-30%, Nb ₂ O ₅ : 0-20%, WO ₃ : 0- 20%, Nb ₂ O ₅ +WO ₃ : 0.1-30%, TiO ₂ : 0.1-15%, F: 0-10%. In order to make the spherical glass particles have the above composition, it is preferable that the non-spherical glass particles also have the above composition. The reason why the glass composition is limited in this way will be explained below. In addition, in the following description of the content of each component, "%" means "% by mass" unless otherwise specified.

_SiO2 is a component that forms the glass skeleton. It is also a component that improves chemical durability and devitrification resistance. The content of SiO ₂ is preferably 20-80%, 50-80%, 50-75%, especially 50-65%. If the amount of SiO ₂ is too small, the chemical durability tends to decrease, and the glass tends to devitrify, which may make production difficult. On the other hand, if the amount of _SiO2 is too large, the meltability tends to decrease. In addition, it is difficult to soften during molding, which may make production difficult.

Al ₂ O ₃ is a vitrification stabilizing component. It is also a component that improves chemical durability and devitrification resistance. The content of Al ₂ O ₃ is preferably 1-30%, 2.5-25%, especially 5-20%. If the amount of Al ₂ O ₃ is too large, the meltability tends to decrease. In addition, it is difficult to soften during molding, which may make production difficult.

B ₂ O ₃ is a component that forms a glass skeleton. It is also a component that improves chemical durability and devitrification resistance. B ₂ O ₃ is preferably 0-20%, 3-19%, especially 5-17%. If the amount of B ₂ O ₃ is too small, the chemical durability tends to decrease. Moreover, the glass tends to devitrify, which may make the production difficult. On the other hand, too much B ₂ O ₃ tends to lower the meltability. In addition, it is difficult to soften during molding, which may make production difficult.

BaO and CaO are alkaline earth elements, and are components that stabilize vitrification as intermediate substances. The total content of these components is preferably 0-40%, 0.1-40%, 0.5-40%, and more preferably 1-30%. The content of CaO is preferably 0-25%, 0.5-20%, particularly 1-15%. If the amount of CaO is too high, the chemical durability tends to decrease, and the glass tends to devitrify, which may make production difficult.

ZnO is a component that reduces the viscosity of glass and suppresses devitrification. The content of ZnO is preferably 0-20%, 0.1-9%, 0.4-7%, especially 0.6-5%. If the amount of ZnO is too large, the chemical durability tends to decrease, and the glass tends to devitrify, which may make production difficult.

Li ₂ O is a component that reduces the viscosity of glass and suppresses devitrification. The content of Li ₂ O is preferably 0-10%, 0-9%, 0-7%, particularly 0-5%. If the amount of Li ₂ O is too large, the chemical durability tends to decrease, and the glass tends to devitrify, which may make production difficult.

Na ₂ O is a component that reduces the viscosity of glass and suppresses devitrification. The content of Na ₂ O is preferably 0-30%, 0-25%, 0-20%, particularly 0-15%. If there is too much Na ₂ O, the chemical durability tends to decrease, and the glass tends to devitrify, which may make production difficult.

K ₂ O is a component that reduces the viscosity of glass and suppresses devitrification. The content of K ₂ O is preferably 0-30%, 0.1-25%, 0.5-20%, especially 1-15%. If the K ₂ O content is too high, the chemical durability tends to decrease, and the glass tends to devitrify, which may make production difficult.

Nb ₂ O ₅ is a component that can adjust the refractive index and Abbe number. The content of Nb ₂ O ₅ is preferably 0-20%, 0.1-15%, 0.5-10%, especially 1-5%. Too much Nb ₂ O ₅ tends to devitrify the glass.

_WO3 is a component that can adjust the refractive index and Abbe number, and is a component that reduces the viscosity of the glass. The content of WO ₃ is preferably 0-20%, 0.1-15%, 0.5-10%, especially 1-5%. Too much _WO3 tends to devitrify the glass.

The total amount of Nb ₂ O ₅ and WO ₃ is preferably 0.1-30%, 0.1-25%, 1-20%, particularly 2-10%. If the ranges of these components are limited as described above, it becomes easier to adjust the refractive index and Abbe number, and it becomes less likely to be colored. Moreover, it becomes easy to suppress the devitrification of glass. Furthermore, it becomes easy to obtain glass with high chemical durability.

TiO ₂ is a component that can adjust the refractive index and Abbe's number, and is a component that reduces the viscosity of the glass. The content of TiO ₂ is preferably 0.1-15%, 0.1-12%, 0.5-10%, especially 1-5%. Too little TiO ₂ makes it difficult to obtain the desired optical properties. Moreover, chemical durability tends to decrease. On the other hand, too much TiO ₂ makes it difficult to obtain desired optical properties. In addition, the glass tends to be colored, and the light transmittance tends to decrease.

The total content of Nb ₂ O ₅ , WO ₃ and TiO ₂ is preferably 0.1-30%, 0.1-25%, 1-20%, especially 3-15%. By limiting the ranges of these components as described above, it becomes easier to adjust the refractive index and Abbe number, and to suppress devitrification of the glass. Furthermore, it becomes easy to obtain glass with high chemical durability.

F is a component that can increase the transmittance, especially the transmittance in the ultraviolet region. The content of F is preferably 0-25%, 0-10%, 0-7.5%, 0-5%, particularly 0-3%. Too much F tends to lower the chemical durability. Further, F is highly volatile, and the component sublimated in the spheroidization step S14 may adhere to the glass surface and deteriorate the surface properties.

In addition to the above components, the following components may be included.
MgO and SrO, like BaO and CaO, are components that stabilize vitrification as intermediate substances. The total content of these components is preferably 0-50%, 0.1-50%, 0.5-40%, and more preferably 1-30%. If the content of these components is too high, the chemical durability tends to decrease, and the glass tends to devitrify, which may make production difficult.

<Dental composition>
A dental composition containing spherical glass particles is described. A dental composition corresponds to an example of a resin composition containing spherical glass particles as a filler.

The dental composition is obtained by mixing resin and spherical glass particles in a mixer. The compounding ratio of the resin and the spherical glass particles is "95:5" to "25:75" in mass %. The compounding ratio of the resin and the spherical glass particles is preferably "90:10" to "40:60", more preferably "85:15" to "50:50", and "80:20". ~ "60:40" is more preferable. If the content of spherical glass particles is too low, the dental composition tends to have poor mechanical strength. On the other hand, if the content of the spherical glass particles is too high, the viscosity of the dental composition will be too high and the fluidity will be reduced, making molding difficult. In addition, a three-roll mill, a rotation-revolution mixer, etc. are mentioned as a mixer.

Resins include curable resins such as photocurable resins and thermosetting resins, and can be appropriately selected according to the molding method to be adopted. For example, when stereolithography is used, a liquid photocurable resin may be selected, and when a powder sintering method is used, a powdered thermosetting resin may be selected.

Examples of photocurable resins include polyamide-based resins, polyamideimide-based resins, polyacetal-based resins, (meth)acrylic-based resins, melamine resins, (meth)acrylic-styrene copolymers, polycarbonate-based resins, styrene-based resins, Polyvinyl chloride resins, benzoguanamine-melamine formaldehyde, silicone resins, fluorine resins, polyester resins, crosslinked (meth)acrylic resins, crosslinked polystyrene resins, crosslinked polyurethane resins, epoxy resins, and the like.

Thermosetting resins include, for example, epoxy resins, thermosetting modified polyphenylene ether resins, thermosetting polyimide resins, urea resins, allyl resins, silicone resins, benzoxazine resins, phenol resins, unsaturated Examples include polyester resins, bismaleimide triazine resins, alkyd resins, furan resins, melamine resins, polyurethane resins, aniline resins, and the like.

<Action of this embodiment>
The physical properties of the spherical glass particles of Examples and Comparative Examples will be described with reference to FIGS. 6 to 8. FIG.
Comparative Example 1-1 is a comparative example in which the dispersing step S13 is omitted from the particle production method shown in FIG. Comparative Example 1-2 is a comparative example in which, in the particle manufacturing method shown in FIG. 5, the dispersing step S13 of colliding the aggregated particles against the collision member 531 is replaced with a dispersing step of passing the aggregated particles through an orifice having a small inner diameter. In other words, Comparative Example 1-2 is a comparative example using an airflow shear type disperser instead of a collision type disperser in the dispersing step S13.

Examples 1-1 and 1-2 are examples based on the particle production method shown in FIG. The difference between Examples 1-1 and 1-2 lies in the inner diameter of the nozzle 511 of the dispersion nozzle 50 . In Example 1-1, the inner diameter of the nozzle 511 of the dispersion nozzle 50 is set to "5 mm", and in Example 1-2, the inner diameter of the nozzle 511 of the dispersion nozzle 50 is set to "3.5 mm". Due to the difference in flow passage cross-sectional area in the nozzle 511, the collision speed of the aggregated particles against the collision member 531 is higher in Example 1-2 than in Example 1-1.

As shown in FIG. 6, D50 after performing the spheroidization step S14 is "1.3 μm" for Comparative Example 1-1, "1.4 μm" for Comparative Example 1-2, and Examples 1-1 and 1- 2 is "1.3 μm". That is, D50 of Comparative Examples 1-1 and 1-2 and D50 of Examples 1-1 and 1-2 are substantially the same.

The specific surface area of Comparative Example 1-1 is "27.4 m ² /g" and the specific surface area of Comparative Example 1-2 is "27.2 m ² /g", whereas the ratio of Example 1-1 is The surface area is "16.3 m ² /g", and the specific surface area of Example 1-2 is "15.9 m ² /g". In other words, the specific surface areas of Comparative Examples 1-1 and 1-2 are greater than "25.0 m ² /g", while the specific surface areas of Examples 1-1 and 1-2 are "25.0 m ² /g" or less. This indicates that the spherical glass particles are more spherical in Examples 1-1 and 1-2 than in Comparative Examples 1-1 and 1-2.

The spheroidization rate of Comparative Examples 1-1 and 1-2 is less than "1%", while the spheroidization rate of Example 1-1 is "99%", and the spheroidization rate of Example 2 is "99%". is "98%". In other words, the spheroidization rates of Comparative Examples 1-1 and 1-2 are less than "1%", while the spheroidization rates of Examples 1-1 and 1-2 are "90%" or more. ing. Here, the spheroidization rate of the present embodiment means that when an arbitrary number of glass particles having a particle diameter of "0.5 μm to 2.0 μm" are extracted, spherical particles occupying an arbitrary number of glass particles It is a value that indicates the proportion of glass particles that have been softened. Further, the spherical particles mean particles having a sphericity greater than "0.5" as described above.

FIG. 7 is a photograph of Comparative Example 1-2 after the spheroidization step S14 and before classification, and FIG. 8 is a photograph of Example 1-1 after the spheroidization step S14 and before classification. It is a photograph. It can be seen that in Example 1-1 shown in FIG. 8, the spherical glass particles have a smaller particle diameter than in Comparative Example 1-2 shown in FIG. 7, and the glass particles are spherical.

Next, the relationship between the D50 of the spherical glass particles and the maximum valley depth (Rv) of the dental material will be described with reference to FIGS. 9 to 12. FIG.
Examples 2-1 and 2-2 and Comparative Example 2-1 in FIG. 9 were produced as follows. First, a photocurable resin (polyamideimide) and spherical glass particles with a predetermined D50 were prepared. The glass composition of the spherical glass particles is, in mass %, _SiO2 : 55%, _Al2O3 _: 15%, _B2O3 _: 15%, _K2O : 3%, CaO: 1.5%, ZnO: 1.5% _, _TiO2 : 1.5%, _Nb2O5 : 3.5%, and _WO3 : 4%. Subsequently, the photocurable resin and the spherical glass particles were mixed at a ratio of 70.0 to 30.0% by mass using a mixer to obtain a dental composition. After that, the dental composition was poured into a predetermined mold and irradiated with ultraviolet rays having a wavelength of 365 nm for 20 seconds. Thus, a model of a dental material (hereinafter referred to as a "dental material sample") was obtained by photocuring the dental composition. Here, the diameter of the dental material sample is 20 mm, and the plate thickness of the dental material sample is 0.5 mm. After that, the surface of the obtained dental material sample was lap-polished with No. 6000 (for 10 minutes) in order to reproduce the surface state after the morphological correction polishing. The spherical glass particles of Examples 2-1 and 2-2 and Comparative Example 2-1 were produced according to the particle production method shown in FIG.

As shown in FIG. 9, the surface of the obtained dental material sample was measured for maximum valley depth (Rv) using a fine shape measuring machine ET4000A (manufactured by Kosaka Laboratory Co., Ltd.). Furthermore, as shown in FIGS. 10 to 12, the surfaces of the obtained dental material samples were observed at a magnification of 1000 using an electron microscope (SEM).

As shown in FIG. 9, in Examples 2-1 and 2-2, the D50 of the spherical glass particles was 2.0 μm or less, so the maximum valley depth (Rv) of the dental material sample was 1.0 μm or less. rice field. On the other hand, in Comparative Example 2-1, the maximum valley depth (Rv) of the dental material sample was greater than 1.0 μm because D50 of the spherical glass particles was greater than 2.0 μm.

In addition, as shown in FIGS. 10 and 11, in Examples 2-1 and 2-2, no depressions with a valley depth (Rv) of 1.0 μm or more could be confirmed on the surface of the dental material sample. On the other hand, as shown in FIG. 12, in Comparative Example 2-1, recesses having a valley depth (Rv) of 1.0 μm or more were confirmed on the surface of the dental material sample.

9 to 12, when the D50 of the spherical glass particles is 2.0 μm or less, it becomes difficult for the spherical glass particles to escape from the surface of the dental material sample, so that recesses are less likely to be formed on the surface of the dental material sample. As a result, it was shown that the maximum valley depth (Rv) on the surface of the dental material sample was 1.0 μm or less.

Next, the relationship between the specific surface area of the spherical glass particles and the viscosity of the dental composition will be described with reference to FIG.
Examples 3-1, 3-2, 3-3 and Comparative Example 3-1 in FIG. 13 were produced as follows. First, a photocurable resin (polyamideimide) and predetermined spherical glass particles were prepared. The glass composition of the spherical glass particles is, in mass %, _SiO2 : 55%, _Al2O3 _: 15%, _B2O3 _: 15%, _K2O : 3%, CaO: 1.5%, ZnO: 1.5% _, _TiO2 : 1.5%, _Nb2O5 : 3.5%, and _WO3 : 4%. Subsequently, the photocurable resin and the spherical glass particles were mixed at a ratio of 70.0 to 30.0% by mass using a mixer to obtain a dental composition.

The viscosity of the resulting dental composition was measured with a HAAKEMARS rheometer RS3000.
As shown in FIG. 13, in Examples 3-1 to 3-3 in which the spherical glass particles had a specific surface area of 25.0 m ² /g or less, the viscosity of the dental composition was 1500 mPa·s or less. On the other hand, in Comparative Example 3-1, in which the spherical glass particles had a specific surface area of more than 25.0 m ² /g, the viscosity of the dental composition was more than 1500 mPa·s.

Thus, the dental materials obtained by curing the dental compositions containing spherical glass particles in Examples 3-1 to 3-3 are less likely to contain bubbles. Therefore, the reduction in the strength of the dental material is suppressed. In addition, the sufficient adhesion between the dental material and the cavity prevents the dental material from peeling off from the cavity.

<Effects of this embodiment>
(1) In the method for producing particles, the dispersion step S13 is followed by the spheroidizing step S14. Therefore, in the particle manufacturing method, the spheroidization step S14 can be performed on non-spherical glass particles, not on aggregated particles. Thus, the particle production method can obtain spherical glass particles that are fine and spherical.

(2) In the particle manufacturing method, the dispersion step S13 causes the aggregated particles to collide with the collision member 531 of the dispersion nozzle 50 to crush the aggregated particles. Therefore, in the dispersing step S13, the aggregated particles are easily crushed to primary particles.

(3) In the particle manufacturing method, the spheroidizing step S14 heats the non-spherical glass particles jetted from the dispersion nozzle 50 by applying flames from the burner 30 to the non-spherical glass particles. Therefore, in the particle manufacturing method, the surfaces of the non-spherical glass particles can be easily melted in the spheroidizing step S14.

(4) In the burner 30 , the fuel injection port 48 of the burner nozzle 40 is arranged so as to surround the powder injection port 532 of the dispersion nozzle 50 . Therefore, the burner 30 can heat most of the non-spherical glass particles jetted from the dispersion nozzle 50 with the flame jetted from the burner nozzle 40 .

(5) The spherical glass particles are fine and spherical. Therefore, when it is contained in a resin composition, the contact interface between the spherical glass particles and the resin tends to decrease. As a result, light scattering is less likely to occur inside the resin composition, and light transmission characteristics of the resin composition are less likely to deteriorate. Also, a large amount of spherical glass particles can be contained in the resin. In this case, the resin composition has high mechanical strength. Furthermore, the spherical glass particles are easily mixed with the resin, and the moldability of the resin composition is improved.

(6) The spherical glass particles have a refractive index of 1.48 to 1.62. Therefore, it becomes easier to match the refractive index between the spherical glass particles and the resin. As a result, the resin composition can obtain moderate light transmission properties.

<Change example>
This embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

- Spherical glass particles, as a glass composition, SiO ₂ : 40 to 80%, Al ₂ O ₃ : 1 to 30%, B ₂ O ₃ : 2 to 20%, BaO + CaO: 0 to 20%, Li ₂ O+Na ₂ O+K ₂ O: 0-30%, Cs ₂ O: 0.1-20%, La ₂ O ₃ : 0-10%, ZrO ₂ : 0-5%.

· In the particle manufacturing apparatus 10 , the dispersion nozzle 50 does not need to be accommodated in the burner nozzle 40 . In this case, the injection direction of the fuel from the burner nozzle 40 and the injection direction of the non-spherical glass particles from the dispersion nozzle 50 may intersect.

- The dispersion nozzle 50 may have a structure for crushing aggregated particles instead of the collision member 531 .
- The spherical glass particles can also be used as a filler for resin compositions other than dental compositions. For example, spherical glass particles can also be used as a filler for resin compositions for modeling such as 3D printers. Here, the resin composition may be a thermosetting resin or a photocurable resin such as an ultraviolet curable resin.

10 Particle production device (production device for spherical glass particles)
DESCRIPTION OF SYMBOLS 30... Burner 40... Burner nozzle 47... Rectifier tube 48... Fuel injection port 50... Dispersion nozzle 51... Pipe 53... Nozzle cover 531... Collision member 532... Powder injection port S11... Preparation process S12... Transportation process S13... Dispersion process S14 …Spheroidizing process

Claims

A method for producing spherical glass particles using non-spherical glass particles as a main raw material, comprising:
a dispersing step of passing agglomerated particles containing the agglomerated non-spherical glass particles through a dispersing nozzle to crush the agglomerated particles and ejecting the non-spherical glass particles from the dispersing nozzle;
a spheroidizing step of heating the non-spherical glass particles injected from the dispersion nozzle to spheroidize the non-spherical glass particles.
2. The method for producing spherical glass particles according to claim 1, wherein in the dispersing step, the aggregated particles are crushed by colliding the aggregated particles with a collision member provided in the dispersion nozzle.
3. The method for producing spherical glass particles according to claim 1, wherein the spheroidizing step heats the non-spherical glass particles by applying a flame of a burner to the non-spherical glass particles jetted from the dispersion nozzle. .
In the dispersed non-spherical glass particles,
3. The method for producing spherical glass particles according to claim 1, wherein the particle diameter is 2.0 μm or less when the cumulative value obtained by laser diffraction scattering particle size distribution measurement is 50%.
A burner for processing agglomerated particles comprising agglomerated non-spherical glass particles, comprising:
a burner nozzle having a fuel injection port for injecting fuel;
a dispersing nozzle having a dispersing unit for crushing the aggregated particles and a powder injection port for injecting the non-spherical glass particles crushed by the dispersing unit;
The burner, wherein the fuel injection port is arranged to surround the powder injection port.
Spherical glass particles,
Having a fire-polished surface on the surface,
Spherical glass particles having a particle size of 2.0 µm or less when the cumulative value is 50% in the particle size distribution measured by laser diffraction scattering particle size distribution measurement.
The spherical glass particles according to Claim 6, which have a specific surface area of 25.0 m2 /g or less.
SiO 2 : 20 to 80%, Al 2 O 3 : 1 to 30%, B 2 O 3 : 0 to 20%, BaO + CaO: 0 to 40%, ZnO: 0 to 20%, F : 0 to 25% of the spherical glass particles according to claim 6 or 7.
the spherical glass particles according to claim 6 or claim 7;
A dental composition comprising a photocurable resin.